This invention relates to a heat-drive refrigerating or Rankine cycle apparatus for controlling the flow rate of a working medium.
In a conventional Rankine cycle apparatus, a heat drive cycle system is formed by connecting an expander successively with a condenser, a pump, and a gas generator. A working medium, e.g., a refrigerant in a liquid phase, is delivered from the condenser to the gas generator, where it is converted into a high-pressure gas, and then transferred to the expander. Thus, the expander is actuated by the gas pressure to drive a refrigerating cycle system.
In the operation of the apparatus, the flow rate of the working medium supplied to the gas generator by the pump does not always agree with the flow rate of the working medium consumed at the expander due to variations in the working medium temperature, load conditions, etc., at the gas generator.
Conventionally, therefore, if the quantity of flow supplied from the pump is larger than the quantity of flow passing through the expander, then a liquid refrigerant will be discharged from the gas generator to lower the drive efficiency, or a gas refrigerant will be sucked into the pump. In the contrary case, the liquid refrigerant will stay in the condenser. In either case, the drive cycle would not be able to operate satisfactorily.
Most Rankine cycle apparatus hitherto known are large and massive. They are provided with a gas generator and a condenser of the type which comprises a housing containing a coolant and a spiral water tube disposed in the housing. Heat is exchanged between the water in the tube and the coolant in the housing. The flow of the Rankine cycle is controlled by adjusting the output of a pump for circulating the coolant so that the surface of the coolant in the housing is maintained at a specific level.
With a small Rankine cycle apparatus to which the present invention is applied, however, it is impossible to hold the coolant surface in the housing at a specific level. This is because the coolant flows through the tube of either the gas generator or the condenser since the tube is a finned tube or a double tube.